There is known an augmented reality (AR) technology that displays a virtual image in superimposition at a predetermined position on a captured image of a real-world space. The AR technology is widely used as supporting work of a worker in a workspace such as a factory by displaying work support information that indicates the content of work, the location of a work target, and the like in superimposition on a captured image.
In the AR technology, it is necessary to accurately obtain the position and the attitude of a camera in the real-world space so as to superimpose a virtual image at an appropriate position on the captured image. An example of the method is a method of estimating the position and the attitude of the camera by measuring in advance the three-dimensional coordinates of a feature point on a target object that is a display target of the virtual image, registering the three-dimensional coordinates on a feature point map, and associating the feature point registered on the feature point map with a feature point that is extracted from the captured image.
An example of the method for computing the three-dimensional coordinates registered on the feature point map is a method in which the target object is captured as two images from two arbitrary points of view, feature points are extracted from each image, and the three-dimensional coordinates of the corresponding feature points between the images are computed based on the coordinates of the feature points in each image by using the principle of triangulation.
The following technologies are also relevant to AR. A technology is suggested that determines whether a selected image is appropriate based on the number of feature points, of which the three-dimensional position is estimated, in the selected image and the angle of intersection between light rays that connect the estimated three-dimensional position of the corresponding feature points included in the selected image and the position of feature points in an image frame. A technology is also suggested that determines the reconstruction position of a marker in a three-dimensional space based on the position of image features in a first image and a second image and the attitude of the camera which captures each image. The technology selects at least one of the images as a key image when a reconstruction error based on the reconstruction position and a predetermined position of the marker in the three-dimensional space satisfies a predetermined standard.
Examples of related art include Japanese Laid-open Patent Publication No. 2009-237848 and Japanese Laid-open Patent Publication No. 2013-127783.
Examples of related art include G. Klein et al., “Parallel Tracking and Mapping for Small AR Workspace”, 6th IEEE and ACM International Symposium on Mixed and Augmented Reality (ISMAR) 2007, pp. 225-234, November 2007 and Kento Yamada et al. “Latest Algorithm for 3-D Reconstruction from Two Views”, Information Processing Society of Japan Study Report, vol. 2009-CVIM-168-15, pp. 1-8, 2009.